The invention relates to a method of and an apparatus for reducing the grain size of crystalline explosive, especially hexogen or mixtures containing hexogen, wherein the explosive is dissolved in an organic solvent, the dissolved explosive subsequently is precipitated and crystallized in the presence of water, and then the resulting recrystallized explosive is separated from solvent and water.
In the context of the present application, crystalline explosive, in the first place, is understood to be hexogen (RDX), also octogen (HMX) and nitropenta (PETN), but also any other explosive which is available in crystalline form as well as mixtures of such explosives.
The final product in the preparation of hexogen and other crystalline explosives is obtained in coarse crystalline form. For many cases of application, however, the crystalline explosive is required to be in fine crystalline form, especially if it is a constituent of a propellant charge powder.
In the case of a known method of reducing the grain size, the crystalline explosive is ground in a mill while liquid is being added. The mechanical crushing of the violent explosive is to be classified as dangerous in spite of the addition of liquid. Moreover, with the known method, the separation of the fine fraction can be accomplished with difficulty only.
A method of the kind mentioned initially is already known from European patent application 0 340 188 by means of which the average grain size of hexogen and other crystalline explosives can be reduced to a mean particle size of less than 20 micrometers. With the known method, the explosive, such as hexogen is dissolved in a solvent and water at a temperature between 60.degree. C. and 70.degree. C. and while being stirred. The explosive solution is conveyed into a steam ejector, while being pressurized by nitrogen. In the ejector, crystallization takes place, the solvent evaporating and the explosive precipitating. The precipitated crystalline explosive then is separated in a downstream cyclone. A mean particle size of 8 micrometers is said to be obtainable by the known process.
It is the object of the invention to propose a method and an apparatus by means of which very small grain sizes can be obtained and with which a very high degree of safety in application is achieved.